Locking plug for receptacles and the like



y 1933- w. E. KRUEGER 1,906,929

LOCKING PLUG FOR RECEPTACLES AND THE LIKE Filed Dec. 12. 1929 amen :06

I $wazyaw m1, alum A. Was

duo'mq Patented May 2, 1933 UNITED STATES WILLIAM E. KRUEGER, OF SOUTH MILWAUKEE, MATERIAL COMPANY, OF SOUTH MILWAUKEE,

DELAWARE WISCONSIN, .ASSIG-NOR TO LINE WISCONSIN, A CORPORATION OF LOCKING PLUG FOR RECEPTACLES AND THE LIKE Application filed December 12, 1929.

This invention relates to locking plugs for receptacles and the like.

It is the usual practice to provide a distribution block or service block in buildings or other places which are provided with receptacles for the reception of main fuse plugs and branch line fuse plugs. It has been the practice also, that when a consumer does not pay his electric bill, to open his service. at some point and to thus prevent further consumption of energy.

This'invention has for its object the provision of a plug which cannot be removed from the socket, receptacle, or cut-outs by an unauthorized person and which is so constructed that it may be readily placed within the receptacle, i. e., in place of a fuse plug and which. will, therefore, open the circuit and lock the circuit open.

Further objects of this invention are to provide a novel form of locking plug for receptacles, which is so made that it is easy for an authorized person to insert or remove the plug by means of a simple tool or key member without destroying or injuring the locking plug, but which is so made that two main parts of the plug will positively lock to the receptacle when removal is attempted without the use of the key member.

Further objects are to provide a plug which will inherently lock itself within a receptacle when an unauthorized attempt is made at its removal, and which is devoid of any fragile or delicate parts or diflicultly produced mechanisms, but which instead is so made that it consists primarily of two main members, each of which is of substantial and sturdy construction and which coopcrate to bind or look tightly within the receptacle when the members are manipulated in any mannerother than that resulting from the use of a special tool or key member.

Further objects are to provide a locking plug for a receptacle which is formed of two main members relatively movable and themselves constituting the main body of the plug, such members being externally threaded to cooperate with the usual threaded receptacle, which in the majority of cases normally receives fuse plugs and in which Serial No. 413,465.

these two members are revolubly related, so that if one member is rotated without rotating the other member, a positive locking occurs.

1n greater detail, further objects of this invention are to provide a locking plug which may be inserted in the service receptacle, which normally receives a fuse plug, and which is formed of two insulating discs in axial alignment and held together in a revoluble manner by means of a suitable memher and provided with externally threaded faces adapted to engage the threads of the receptacle and in which a key member 01' special tool is provided, which, when used, causcs thc two members to rotate together as a single unit during the authorized insertion or removal of the plug, an unauthorized attempt to remove the plug result ing in the relative rotation of one of the members with respect to the other, thereby causing the plug to positively lock itself in place.

Further objects are to provide a locking plug which readily lends itself to quantity production, which has a limited number of relatively strong parts and which may be cheaply and easily produced.

Embodiments of the invention are shown in the accompanying drawing, in which Figure l is a sectional view through the receptacle showing the plug in place and showing the key piece about to be inserted, such key piece being partly in section, such view corresponding to a section on the line l-l of Figure 2.

Figure 2 is a face view with the plug in place.

Figure 3 is a view of the key member or special tool.

Figure 4 is an enlarged fragmentary section view showing a modified form of attaching means for joining the two portions of the plug.

To avoid needless repetition in the description and claims, the word receptacle will be employed to indicate a receptacle, socket, cutout, or other device of this general order and it is, therefore, not intended that this term be construed in any limiting sense.

It is the usual practice to provide a distriof the receptacle bution block or fuse block or panel, to which the service wires are attached and from which the distribution wires lead to dill'erent portions of a building, factory or other place where electric service is furnished. This distribution block or panel is provided with a plurality of receptacles which normally receive the fuse plugs.

Referring to the drawing, it will be seen that a receptacle 1 has been shown as provided with a metallic screw threaded shell 2 and a central contact 3 in the usual or conventional manner.

The locking plug consists of an inner disc 4 and an outer disc 5 formed of Bakelite, fibre or other suitable material, preferably 'nsulating material. These discs are revolubly joined by any suitable means, i. e., a rivet, screw, pin or other member may be used. In the form shown in Figure 1, a screw 6 is employed to revolubly and loosely join these members. This screw has the threaded portion of its shank screwed into the outer member 5 and has its head 7 located within a recess 8 formed in the inner member 4. It is to be noted that the end of the screw, as

' shown in Figure 1, abuts against the bottom of the central threaded hole formed in the member 5 and that the head 7 has a slight play in the hole 8, that is to say, the head 7 does not seat against the bottom of the hole 8.

This allows relative rotation of the members 4 and 5 and also allows a slight separation of the members to occur, as will hereinafter appear in greater detail.

The members 4 and 5 have externally threaded peripheries for cooperation with the threaded shell 2.

The two members 4 and 5 are respectively provided with holes 9 and 10, which align when these members are in contact as shown in Figure 1. It is also preferable to provide the member 5 with a notch or a hole 11. The key member or s ecial tool for inserting or removing the loc ng plug may consist of a disc-like body portion 12, provided with an ear 13 adapted to fit into the notch or recess 11 and provided with a thumb piece 14. A pin 15 is firmly socketed within a disc-like body portion 12 and projects therefrom as shown in Figure 1. Preferably the key member is moulded with the pin in place. Obviously, any other suitable means could be used for securing the pin to the body of the key member.

In inserting the plug in the receptacle, it is merely necessary to slip the pin through the aligning holes 9 and 10, the ear or shoulder l3 seating within the recess 11. Thereafter the key member may be rotated to screw the plug into the receptacle. During this operation, the members 4 and 5 are held against relative rotation and the two members act as a unit and are easily screwed into the receptacle. However, after the key member is removed, if an unauthorized attempt is made to unscrew the plug, it is obvious that the only member that can be reached is the outer member 5. Consequently, if a screw driver or other usual tool is employs in an unauthorized attempt to unscrew the plug, it is apparent that the member 5 will rotate relatively to the member 4. As soon as the head 7 of the screw contacts with the base of the hole 8, it is apparent that the two portions of the plug will jam as further separation cannot occur. Consequently, the two members of the plug will tightly interlock with the threaded portion of the receptacle and positively prevent the unauthorized removal of the plug. In addition to this, it is very unlikely that an unauthorized person will discover the hole 9 for it is formed in the inner member 4 and, consequently, there is very little chance that he will be aware of the necessity of maintaining the holes 10 and 9 in alignment. In addition to this, the slightest relative motion of the two members 5 and 4 will prevent alignment of the holes 10 and 9.

It is apparent that the maximum strength for the structure is obtained as there are only three main parts to the locking plug, namely, the members 4 and 5 or the screw or connecting member 6. No delicate or fragile mechanism is employed in the construction of this plug. Instead very sturdy and relatively large parts are all that are needed. The net results of this manner of constructing the plug are extreme strength coupled with simplicity of construction.

It is apparent that other means could be used to revolubly join the members 4 and 5 without departing from the spirit of this invention. One of several methods of joining these members is indicated in Figure 4. In this form of the invention, the screw differs slightly from the screw (5, previousl described in that it is provided with a s ank having an enlarged portion 16 and a reduced threaded portion 17 which latter portion is screwed into the member 5, the shoulder between the portions 16 and 17 abutting against the inner face of the member 5. The head 18 of the screw is located within the hole 8 formed in the member 4 and has a slight amount of play therein, exactly similar to the construction previously described.

It will be seen that this invention provides a locking plug which is strong, sim 1e, easy to produce and easy to use. it is a so to be noted that this invention provides a locking plug which is highly effective in use and which will successfully prevent unauthorized attempts at its removal.

While this invention has been described as primarily directed to means for lockin the service open, it is apparent that the loc ing plug could be constructed in a manner to short circuit the terminals of the receptacle,

mo est if it were so desired. Obviously, the only change that need be made is to form the memher 4 of conducting material. This would connect the central contact of the receptacle with the threaded shell. The construction of the plug would be identically the same with this single exception.

Therefore, although invention has been de scribed in considerable detail, it is be understood that such description is intended as illustrative rather than limiting, as the invention may be variously embodied and is to be interpreted as claimed.

I claim 1. The combination of a screw threaded receptacle and a locking plug comprising two circular, externally screw threaded members adapted to be screwed into said receptacle, a pin revolubly joining said members and permitting a slight separation of said members, and means for holding said members in a predetermined position during the insertion of said members into said receptacle, the joint axial length of said members being less than the axial depth of said receptacle whereby said members may be screwed into said receptacle to a position below the outer surface of said receptacle.

2. A locking plug for a receptacle provided with an internally threaded shell, said locking plug comprising a pair of circular discs formed of insulating material, means revolubly oining said discs, said discs having threaded peripheral faces adapted to engage the threads of said receptacle, and means for temporarily holding said members in a predetermined position during the insertion of said members into said receptacle.

3. A locking plug for an internally threaded receptacle, said locking plug comprising a pair of discs having their peripheral faces threaded and adapted to engage the threads of said receptacle, and an axially positioned member revolubly joining said discs, said discs having holes adapted to align when said locking plug is screwed into the receptacle.

4. The combination of an internally threaded receptacle, a locking plug formed of two separate members revolubly joined and provided with external threads, one of said members forming an outer member and the other of said members forming an inner member, the outer member closing said receptacle against use, said members having holes adapted to align during the insertion of said plug into said receptacle, said outer member having a shoulder, and a key member having a pin adapted to enter the said holes of said members and having a shouldered portion adapted to engage the shoulder of the outer member.

5. A locking plug comprising a pair of relatively movable, circular members, a headed, axially arranged member joining said circular members, one of said circular members having a recess for the reception of head of said axially arranged member and permitting slight separation of said circular members, and means for temporarily holding said circular members locked together during the insertion of said circular members into a receptacle, said members closing said receptacle against use.

6. A locking plug for an internally threaded receptacle, comprising an outer circular member, an inner circular member, a bolt revolubly joining said members and permitting limited bodily separation of said members, said members having holes adapted to align during the insertion of said plug into the receptacle, said members closing said receptacle against use.

7. A locking plug for areceptacle having two electrical contacts and having an inter nally threaded portion, said locking plug comprising two revolubly joined members adapted to enter the internally threaded portion of said receptacle and automatically locking within said receptacle and closing said receptacle against use, and extending across one of said contacts and preventing electrical connection with said last mentioned contact.

In testimony whereof, the signature of the inventor is aiiixed hereto.

l/VILLIAM E. KRUEGER. 

